This invention relates to bandages carrying cement compositions comprising ion-leachable inorganic compounds preferably in the form of glasses. In particular, this invention relates to coating a suitable substrate with such cement compositions to produce an orthopedic bandage.
Ion-leachable inorganic compounds such as the oxides of aluminum, zinc, magnesium, and calcium have been intermixed with other components such as silica and formed into glasses which, when combined with such hydrogen-donating compounds as acids, will set up into a cementitious mass. The mechanisms for the reaction has been described by Alan D. Wilson, et al. (Journal of Dental Research, Volume 58, No. 3, at pps. 1065-1071, March 1979), and can be presented by the generic equation: ##EQU1## Cements utilizing this mechanism have generally taken the form of glass powders incorporating the ion-leachable inorganic. These are reacted with acid solutions such as aqueous, poly(carboxylic acid) solutions to form a salt hydrogel structure which sets up to a hard mass. Such cement-forming compositions have been suggested for use in application such as dental cements and for orthopedic purposes; i.e., casts and splints. For example, a fluoroaluminosilicate glass powder has been suggested for use as the ion-leachable component for dental cement as in British Pat. No. 1,316,129. Similarly, such a composition has been suggested for use in orthopedic surgery in U.S. Pat. Nos. 4,143,018 and 4,043,327.
Traditionally, the orthopedic practitioner is accustomed to being provided with a dry roll of bandaging material impregnated or coated with a cementitious composition, generally plaster of Paris. The practitioner then dips the roll into a bucket of water, wraps the bandage around the limb of the patient where, after a short time, the bandage sets to a rock-like hardness.
In attempting to emulate this cast-forming procedure and employ ion-leachable cement compositions such as have been used in the dental field, certain difficulties have been encountered. Firstly, the method employed by the dental practitioner cannot be readily translated to the orthopedic field. In dentistry, the cementitious composition is provided in two parts; the ionomer glass component and an aqueous solution of the poly(carboxylic acid) component. The dentist, requiring only small quantities of a cementitious mass at any given time, can easily mix these two parts just at the time of use without any great inconvenience. Unfortunately, this method is totally impractical for the orthopedist in that he requires large quantities of cementitious mixture at a given time and his difficulties are further compounded by the fact that he requires this cementitious material in the form of a wrapping for a limb.
In view of the above, it has been suggested that powderous forms of the ionomer glass, the poly(carboxylic acid) and any other additives such as accelerators, modifiers, deodorants, or the like, be intermixed and held in suspension in a non-aqueous non-reactive organic liquid. This suspension can then be coated onto a bandage substrate such as gauze and, when dried, will adhere to the substrate to produce a dry orthopedic bandage. The bandage can then be used in the same manner as those plaster of Paris bandages with which the orthopedist is most familiar; i.e., it may be dipped in water to become activated (begin the gelation reaction) and then wrapped around the limb of the patient and set into a rock-like cast. It has been variously suggested that such non-reactive organic liquids could be, for example, methyl ethyl ketone, methylene chloride, or cyclohexane (See U.S. Pat. No. 4,043,327, issued Aug. 23, 1977, to Potter, et al.; Dutch Specification No. 7604906, published Nov. 16, 1976, in the name of Smith and Nephew Research Ltd. and Pilkington Bros. Ltd.; South Africa Application No. 747391 published Nov. 15, 1974, in the name of National Research Development Corporation; and British Provisional Specification No. 55471, published in 1973).
While such prior art suggestions can be utilized and will produce a usable bandage, several drawbacks are encountered in an attempt to employ this method to the high speed production of commercially available quantities of orthopedic bandages. For example, it has been discovered that only a very limited amount of the solid material can be held suspended in the liquids suggested by the prior art. Accordingly, in order to provide a bandage carrying the requisite quantity of cementitious composition an impractically large quantity of the suspension must be deposited into the bandage substrate requiring, in turn, a considerable effort in both processing time and energy requirement to drive off the liquid and produce a dry bandage. Since these liquids are relatively expensive, a commensurability large amount in time and energy is required to recover and recycle the liquid driven off. Further, it has been discovered that while a limited quantity of the solid cementitious material can be induced into suspension in the suggested liquids, such suspensions are not stable and instead settle out after an impractically short period of time thus requiring that the coating suspension either be prepared immediately before use or else that elaborate stirring and agitation means be provided to keep the solids in suspension during the coating process.
Still further, it has been discovered that after the suspending liquid has been driven off, the solid materials do not cling readily to the bandage and instead dust off in obvious detriment to the entire process.
In view of the above drawbacks, an improved method for providing an orthopedic bandage with an ionomer cement composition is required.